Riot police in St Petersburg, Russia's second city and Putin's home town, detained Boris Nemtsov and Nikita Belykh, leaders of the Union of Right Forces (SPS) party who are both running in the December 2 election. They were later released.

The protests came a day after police detained opposition leader and former world chess champion Garry Kasparov in Moscow -- a move the United States condemned on Sunday as part of "aggressive tactics" by authorities.

"We are troubled that Garry Kasparov and other leaders of the opposition have been arrested and detained," said White House National Security Council spokesman Gordon Johndroe.

Kasparov, leader of the Other Russia group, was among 60 detained in the 3,000-strong Moscow march, activists said.

In St Petersburg, this correspondent saw riot police beating activists with batons and their fists before forcing them into police buses.

Dozens more were detained outside the Winter Palace, the residence of the Tsars, and at another rally in the city centre.

"They have forbidden us from discussing Putin," Nemtsov told the crowd. "But we have come here today to ask Mr Putin and the authorities why is there so much corruption in the country?"